STEREOLOGICAL STUDY OF THE ULTRASTRUCTURAL-CHANGES INDUCED BY CHRONICALCOHOL-CONSUMPTION AND DEHYDRATION IN THE SUPRAOPTIC NUCLEUS OF THE RAT HYPOTHALAMUS

We have previously shown that prolonged alcohol ingestion leads to neu ronal loss in the supraoptic nucleus of the rat and that the surviving neurons, mainly the vasopressinergic ones, display marked increase in volume. In an attempt to establish correlates for the volumetric alte rations we have studied the organelles of supraoptic nucleus neurons i n three groups of rats ethanol-fed, pair-fed, and dehydrated, in all c ases treated from 2 to 12 months of age. The volume and surface area o f the rough endoplasmic reticulum and Golgi apparatus, and the volume of nucleoli and neurosecretory granules were estimated on the basis of the respective volume and surface densities. The volumes and surface areas of all quantified organelles were increased in both alcohol-fed and dehydrated animals, although the increases were greater in the for mer group. Changes in the organelles studied are commonly regarded as reliable indicators of the neurosecretory activity of magnocellular ne urons. Thus, our results suggest that under conditions of chronic alco hol exposure, the synthesizing activity of the surviving supra-optic n eurons is augmented to compensate for the alcohol-induced neuronal los s and/or as a consequence of the alcohol-induced hyperosmolality. Chan ges in the transport and release of the neurosecretory material cannot , however, be ruled out as an additional cause of neuronal enlargement .